Many chemical and biochemical detection methods have been developed that require costly and sensitive reagents. Applications for these detection methods are sought where the detection device must be compact. These are some motivators for the development of microfluidic devices, which encompass analytical systems where reactions and detections are performed on fluids or suspended solids carried in micro-scale channels. The very small amounts of materials used for these reactions and detections allows for, among other things, cost-effective analysis and the use of instrumentation in settings where space is limited.
Many detection methods involve determining spectroscopic properties of light from a sample, where the light may be scattered from a sample, or emitted as chemiluminescence by a chemical process within a sample, or transmitted through a sample, or selectively absorbed by a sample, or emitted as fluorescence from a sample following excitation.
Photomultiplier tubes (PMTs) are commonly used to detect, for example, fluorescent signals. Known systems employing PMTs are constrained by the inability of a PMT to discern the frequency of incident light. To provide this sensitivity, the system must also incorporate an optical filter ahead of the PMT, chosen to select only the particular wavelength of interest. Systems using PMTs for detection of multiple colors require a means to distribute the observed light among several PMTs, one for each discrete color to be detected, each of which must have its own particular filter. A PMT based system for measuring emissions from several samples at once would have to duplicate all of this distribution, filtering and detection hardware for each sample to be observed. Additionally, any change in the colors of light to be detected would require the replacement of the corresponding filters.
Accordingly, there is a need for a system that is able to efficiently perform a large number of high-speed, discrete measurements of arbitrary spectroscopic properties in very small targets, as is provided by the following invention.
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